Magnetic disk drives comprise a rotating magnetic disk and a slider which has a magnetic read/write device mounted thereon to constitute a magnetic head and is supported by a suspension. The slider runs over the magnetic disk, allowing the magnetic read/write device to read/write magnetic information from/to the magnetic disk. The slider is designed to fly as an air-lubricated bearing by using the wedge film effect of air so as not to cause direct solid contact between the magnetic disk and the slider. To raise the recording density in the magnetic disk drive and consequently increase the storage capacity of the drive or reduce the size of the drive, it is effective to raise the linear recording density by reducing the distance between the slider and the magnetic disk, that is, the flying height of the slider.
The flying height of a slider may become lower than targeted since it depends on process fluctuations and operating environmental conditions such as ambient pressure and temperature. Therefore, when designing a slider, it is usual to set a margin to the flying height so that the slider does not make contact with the disk even in the worst case. If the slider can adjust the flying height according to the operating environment on a head by head basis, it is possible to widely reduce the distance between the magnetic read/write device and the magnetic disk by eliminating the margin while preventing contact between the slider and the disk.
In Japanese Patent Publication No. 1993-20635 (“Patent Document 1”), a technique is described in which a think film resistor, arranged between the upper and lower magnetic poles of an inductive thin film magnetic head, is energized, i.e., heated as necessary in order to project the front ends of the magnetic poles through thermal expansion and consequently reduce the distance between the front ends and the magnetic disk. Described in Japanese Patent Publication No. 2004-335069 (“Patent Document 2”) is a technique to set the sheet resistance of the heater's heating portion higher than that of the lead portion so that heat is generated more from the heating portion than from the lad portion.
To implement a heater in a think-film magnetic head, its heating portion and lead portions are formed by thin-film fabrication process. Generally, the heating portion is formed and then the lead portions are formed so as to respectively overlap the contact regions of the heating portion. This causes inter-film diffusion as a variable factor for resistance. If resistance increases due to inter-film diffusion where a lead portion is bonded to a contact region of the heating portion, this increases the resistance of the hater heat and the heat loss in the lead portion. In this case, it may be impossible for the heating portion to generate as much heat as intended. In addition, the resistance variation of the heater makes it impossible to reduce the flying height as intended. In the above-mentioned techniques, the resistance variation of the heater due to inter-film diffusion is not taken into consideration.
In manufacturing a magnetic head slider provided with a heater for controlling the flying height, the terminal portions and the lead portions of the heater are formed separately. Therefore, resistance may increase due to inter-film diffusion where a lead portion is stacked on a lead portion, resulting in an increased heat loss. Consequently, if the heating portion does not generate as much heat as designed, it is difficult to lower (control) the flying height as intended.